Automatic trunking system.



E. A. R'EINKE. AUTOMATIC TBUNKING SYSTEM.

APPLICATION FILED NOV. l8. 19M.

Patented 0013. 9,1917.

2 SHEETS-SHEET I Irvvemtofi ne fi'. Rain/7G6 E a B xiwf E. A. REINKE.AUTOMATIOTRUNKING SYSTEM.

Patented Oct. 9, 1917.

APPLICATION FILED NOV. 18. 1914.

m w 6 fi% F E W n vrr D STATES PATEN 1 oFEIoE,

EUGENE A. REnvK 'oE nocnEsr n, roan, Assieivon r sTnoMBEne-oaitiisoiv fTELEPHONE MANUFACTURING GOMEANY, QB noGHEsrEa, NEW Y BK, A con-POBATION' OF NEW YORK.

mat-Am TRUNKIitG s'rsTEn.

specification of Letters ia'tent.v Oct, 9, 3

Application filed November 18, 1914. Srial No. 872,689.

T 0 all whom it may concern: Be it known that I, EUGENE A. REINKE, acitlzen of theUmted St2lt6S,I 6S1Cl1I1g at Rochester, in the county ofMonroe and State of New York, have invented a certain new and useful.Improvement in Automatic Trunking-Systems, of which the following is afull, clear, concise, and exact-description, referencebeing had to theaccompanying drawings, forming a part of this specification.

The subject matter automatic trunking system.

The invention is especially applicable to trunk lines running, betweencentral switchboards and private branch exchanges.

In manual systems, the practice heretofore has been to-provide a certainnumber of lines having the usual directory and switchboard numbers,these lines being assigned to the private branch exchange; Hence, it hasbeen necessary to furnish the operators at the central switchboard witha list of the number of lines which are connectedto a given privatebranch eiichange.v In making.

thesame to ascertainif it were busy. Inasmuch as a number of the linesto a private branch exchange are often added after. a

considerable period, it is impossible to select consecutive numbers and,as a result, the

lines leading to a private branch exchange The object of the presentinvention is to provide a trunking system for private branch exchangeservice which will automatically select an idle trunk from a number oftrunks leading from the central switchboard to the private branchexchange.

Another object or the invention is to provide an improved busy testwhich will relieve the operator of the duty of manually testing thetrunks to ascertain their busy or idle condition.

A still further object is to provide a meter for registering the numberof times that a call 'to the private branch exchange was initiated butcould not'be completed, due to the busy condition of all the trunks.

In the accompanying crawing's, the single figure, comprising parts 1 and2placed on of this invention is an terminals of the group of lines ortrunks lead mg to a given private branch exchange,

Sheets 1 and 2, respectively, illustrates diagrammatically a systemembodying my invention.

A number of jacks 1 are located at various positions on the mainswitchboard corresponding to their directory-numbers. and

are each connected to selecting switches-2, which have access tocontacts 3., 4 and 5 forming the line and private terminals'ot. thetrunks 6, 7, leading to the private branch exchange. Each line jack 1,by means of its switch 2, has access to all of the line an extra pair ofcontactslO, one of which;

75 as indicated at 11, 'the other contact being is connectedto thegroundedside of battery,

connected through the springs 12, 13, ofthe double wound testing relay1%, through the selecting relay '15, to battery '13, over the bus-bar16.

The contacts'prings 10 also close a circuit for the low wound relay 18byway of. the wire 19, through th'e'windings of the relay 18, springs20, 21 and through the normally closed springs 23, 24 of the busygroup'relay 25-, .to battery by way of bus-bar 16.

The selecting relay 15, by closing-a. pairs of contacts 30, closesa'circuit for the stepping magnet 31 to start the selecting switchin-its search fora set of idle trunk contacts, the circuit for thestepping magnet 31 being formed from the battery B, through theinterrupter 32, through the normally closed contacts 28 of the relay 25,winding of stepping magnet '31, through the contacts 30 of the relay 15,these contacts being closed by the energization of said relay, and.-through the normally closed contacts 33-, 3: to the grounded side ofbattery,

The energization of the selecting relay15 closes a pair of contacts 39which places the winding 36' of the double .w'ound relay 1 1 in contactwith the private segment 40 of the selecting switch, a circuit beingformed from the grounded side of battery, through the contacts 39,winding 36 of relay 1 1, nor mally closed contact springs 43 of thestepping magnet 31 to the private segment 40.

As soon as one of the switch arms connects the private segment 40 withan idle private terminal 5, the winding 36 will be energized to breakthe circuit 01 the stepping magnet.

Let it be assumed that the idle trunk 6, 7, having the terminals 3, 4-and the private contact 5, is selected by such operation the winding 36of relay It will then be energized over the following circuit: groundedside of battery B, contacts 39 which are held closed by the energizationofrelay 1'5, winding 36 of relay 1%, contacts 43, private segment 10,private contact 5, winding 44 of the private relay as to battery overthe bus-bar 16. The relay 1% is thereby energized opening the contacts33, 34, and

closing'the front contacts 3 35, to form a shunt for the winding 36,and, at the same time, placing direct ground upon the private contact 5so that the trunk corresponding thereto will be non-selectable by anyother switch 2 corresponding to a different ack 1 on the mainswitchboard. As the automatic switch is nowinactive, the line segments11, 12, are in contact with the terminals 3, 1, of the trunk 6, 7,leading to the private b 'anch exchange. Energization of the relay l ibreaks the contact at springs 12, 13, and makes contact between springs9 and 12, this set of springs being a make-beforebreak device. As aconsequence, the winding 37 will be energized by current flowing frombattery B, through the winding 37 make-before-break contacts 9 and 12,through the contact pair 10, to grounded side of battery 11 to form alocking circuit. The circuit for relays 15 and 18 is thereby broken andthese relays are deenergized. The winding 36 of the testing relay 1% isat this time deprived of current, but the grounded contact 34: is heldagainst contact 35 to maintain a test potential upon the privateterminal 5.

The private relay 45 is also held energized during the busy condition bycurrent flow ing over the grounded contact 34 for a purpose to bedescribed later. The testing relay 14', in addition to closing its ownlocking circuit, closes the sleeve contacts 50 in the line 49 connectingthe sleeve spring of the ack 1 with the segment 42 of the selectingswitch. The deenergization of the selecting relay 15 closes the tipcontacts 51 52 in the line 48 connecting the tip spring of the jack 1with the segment ll of the selecting switch. Connection is therebyestablished from the plug 8 of the operators cord circuit, through theselecting switch, to the private branch exchange. The operator isapprised of the completion of the connection by lighting of thesupervisory lamp 54, when the line circuit is completed, the circuit oflamp 54 being closed by energization of the tip relay 55 over the tipside of line, through the contacts i13 of the automatic switch, andthrough the winding 57 of the cut-otf relay 56 to the grounded side ofbattery.

The operator then applies ringing current from the generator 59 to theline by means of the ringing key 60. As soon as the call is answered atthe private branch exchange, the sleeve supervisory relay 61 will beenergized and the supervisory signal 54: obliterated.

In case the lines 6 and 7 had been busy, the terminal 5 would have beensubject to a test potential from a grounded contact 3 of some otherswitch, thus short-circuiting the winding 36 and preventingenergization.

If all the trunks leading to the private branch exchange are busy, and acall is initiated at the central station, the operator and the callingsubscriber will beapprised of the busy condition ot'all of the trunks inthe following manner: A. busy signal 62 may be installed on the mainswitchboard adjacent the jack 1 connected to the selecting switch 2.Lighting of this lamp 62 indicates that all ofthe trunks are selectedand are busy. A meter or register It is provided for recording each suchoccurrence, in. order that the central station may be apprised of theadequacy of the number of trunk lines to a given private exchange. Incase all of the trunks are busy and a call is initiated, the switch 2will not be caused.

to rotate uselessly but will fail to start, inasmuch as the steppingcircuit will bee pen at the contacts 28. The relay 1 10f each busy jack1 is energized at this time, and

the grounded contact 3% closes the circuit for the winding 44:.of therelay 45 to maintain the same in'energized condition. Tnas much as eachone of the relays 15 associated with their respective lines is energized, the normally open contacts'63 thereof will be held closed. Thecontacts 63 are all connected in series so that a circuit will not becompleted through them until all of the trunk lines are busy, but uponsuch occurrence a circuit is formed for the busy group relays 25 and 65in parallel. The energization of the relay'25 has opened the contacts 28so that no movement of the s itch 2 will be caused. The jack switch 10closes the circuit through the relay 15 to cause it to operate itscontacts, but, as above explained, the relay 1% cannot be energized, dueto the short-circuited or open condition of its winding 36. The circuitfor the relay 18, which was previously closed at the contacts 23, 2%, isnow closed through the contacts 24, 26, in series with the registercontrolling relay 66. The relay '66 is wound to a high resistance,approximately 2000 ohms, while the relay 18 is wound only to about 200ohms resistance. In consequence of this the relay'66 energizes beforethe relay 18 is energized and-closes the contacts 67, which control thecircuit of the relay 68. Relay 68 connects the terminal ofrelay 18to'battery directly by. :way of the spring 69,, so

that relay 18 is operated. This results in a closing of themake-before-break contact- 22.

at'the relay '18 t0..lock the circuit'of there-f lay 18 for the purposeofgivingabusy 'signal, as will be described later.

The energization of the relay 68, which was caused by .an insertion ofthe plug Sin the jack 1 at the time that .all of. the trunk lines werebusy,'.causes a "registration to be made on the register R shown at theleft of ingit to open itscontact 67 and de'energize.

therelay 68. I

Energization of the relav 18, as above EX?- plained, closes theCOntflCb'piLlI'S 72;, 73, the I first pair controllingthe circuit oftheilamp flasher 7%. connected to the busy signal 62.

The circuit of this signal is formed from grounded side-ofbattery,through the interrupter 74,through. the contacts 27 of .the relay 25,through the contact 72 of the relay 18, through the signa-lu62 tobatteryBr. 1-.

' If desired, a busy signalmay .benauto' matically given directly tothe-calling sub-.1 scriber to inform him of the condition-of the privatebranch exchange circuits; "This is accomplishedby the connection lot-thebusy testmachine 75 to theltipside of' the line over the followingcircuit: groundedside of battery, interrupter 7 5, contacts 76, whichare held closed at this time by the ener'gization of relay 65',contact73'oii' the relay 18,. contacts 51, 53 of the relay 15 to thetipside" of theline, thr'oughthe tiprelayof the cord.

circuit to :the battery B.- As the circuit is opened and closed at thebusy machine :75, theslampfii will beflashed and a busy'to'ne.

may be given oven-the:callingline.

lVhen these special trunkcircuits are to be used onlines at privatebranch exchangesfor night service, a regular line equipment is placed atthe main exchangefas indicated in the drawings. Thisscomprises a springjack 77 andline signal 78. Aswitch 80, controlling the circuit for thesignal lamp 78' may be closed when it is desired to use the trunk 6, 7,as a llne for calllng the central station. A relay 79 is connected incircuit with the winding 58 of the cut-off. relay 56 in series with thecontacts 82, 83, and the sleeve side 7 pf the trunk line, the otherwinding 57 of therelay 56 beingconnectedv from the grounded side ofbattery rtothe tip side of the trunk 6, 7, and it can be seen that acircuit will be closedthrough the relay 7 9 and v56'when the terminalsof the trunk 6, 7,

are .closed at the private,hranchzexchange as .in the. art. .Due to thefactzthat"the:relay a5 is connected in parallel With the relay-56,manual selectlon of a trunk line WllliI'GIidBl; the same busy1Il;l3l16-.'S2111 16 manner as-a-con nection of anautomaticswitchthereto,I the;

contact 63 being closed at this time, so that.

if part of the-lines are. used toriealling the central exchange, .andtheremainder are busy, due to, incoming calls over- .automatic switches 2,the fact. of an incoming call be ing initiated 'duringthe-timewhen, allof.

the lines. are thus busy. will be recorded on" the-register-R. 1 w- ;f

A brief description of theopera tion is as follows: Insertion of a.plug- Sin thejack 1 energizes the relay-115 to start the automaticswitch in a searchgjforail'. idle-s t 015 runk.

terminals. This, switch contii'nies i-unt-il a set; of idle contact/sisfound, at which time the relay 11 will be energized to place busy potential on the p-rivatecontacton the selected trunk, the correspondingrelay. 45 being energized to close the series contact 63.. zzconnectionbeing made through the automatic switch with anidle trunkis-i'n'dicatedto the operatorby the lighting other supervisory lamp on accountofcurrent fiowingoverthe tip side of theyline through the relay. Ringingcurrent is applied'to the-trunk line, and the private branch exchangeIBSPODdS ill the usual manner. As soon as .all? the. trunks are renderedbusy by being selected or by serving as calling lines, the seriesofcontacts 63-will be closed to energize the busy group relays65-andc25whichare com mon to the group oftru-nks corresponding to each oneof'thejacks 1. I,-:at 'this'time, the incomingcall is initiated byinsertionof a plug 8' in'idle jack 1,a switch2-corresponding theretowill not be operated, but-instead a connection will be made through.theibusy, signal 62 to apprise the'operator oftherbusy'r condition ofall-thetrunks to theprivate ofbusy tests by the operator.

It isto be understood that'any number of telephones may be connected atthe private branch exchanges in the well-known manner. It can' be seenfrom the above that I-have provided a system in which only a limitednumber of jacks need to be provided throughout a' multiple switchboardfor a plurality of trunk connections at a private branchexchange. As theselection of the trunks is automatic it obviates the making torrecording the fact of an unsuccessful call-tor a private branchexchange, due to busy 'condition, is especially valuable in furnishingstatistics upon the adequacy of existingconne ctions between a privatebranch exchange and the central oiiice. The automatic selectingarrangement does not preventthe trunk lines from being used as callinglines, thus securing a maximum efli ciency of the apparatus employed.

It will be apparent to those skilled in the art that my invention is notto be construed as being dependent upon any of the details which Ihave'set forth above, but

that the invention may be practised in various forms, and may be subjectto numerous modifications, all of which I consider to come within thespirit and scope of my invention. w v V VVhat'Iclaimisr V I '1. Incombination, a central exchange switchboard, a plurality of telephonelines terminating in multiple jacks on said switchboard, said jacksbeing arranged in regular predetermined numerical order, cordcircuitsfor interconnecting said lines, a private branch exchange, saidexchange being designated by a regular directory number, a plurality oflines between the central andisaid private exchange switchboard,multiple jacks corresponding in numerical position on said switchboardto the directory number or said private branch exchange, automaticlineselecting switches connected to said jacks,each switch :being set intoaction to select one of the idle lines between the exchanges when a plugis inserted in the corresponding jack, and means controlled by the busycondition of all of said trunks for preventing movement of said switch.I V

2. In combination a central exchange switchboard, a plurality oftelephone lines terminating in multiple jacks on said switchboard, saidjacks being arranged in regular predetermined numerical order, cordcircuits for interconnecting said lines, a subscribers station beingdesignated by a regular directory number, a plurality of lines betweenthe central switchboard and The means 1 said subscribers station,multiple jacks corresponding in numerical position on said switchboardto the directory number of said subscribers station, automatic lineselecting switches connected to said jacks, each switch being set intoaction to select one of the idle lines between the exchange and thesubscribers station when a plug is inserted in the corresponding. jack,a controlling circuit closed upon the insertion of a plug in said jackfor causing said switch toselect an idle line, and means controlled bythe busy condition of all of said lines for opening said controllingcircuit.

3. In combination a central exchange switchboard, a plurality oftelephone lines terminating in multiple jacks on said switchboard, saidjacks being arranged in regular predetermined numerical order, cordcircuits for interconnecting said-lines, a private branch exchange, saidexchange being designated by a regular directory number,-a plurality oflines between the central and said private exchange, multiple jackscorresponding. in numerical position on I said switchboard to thedirectory number of said private branch exchange, automatic lineselecting switches connected to said jacks, means controlled by theinsertion of a plug in each jack for movingthe corresponding switch toselect an idle line, a private relay for each line, said relay beingenergized by the connection of a jack with the corresponding line, aninterrupter circuit for advancing said: automatic switch, a seriescircuit having contacts controlled by said private relay, relay in saidcircuit for opening said inter-. rupter circuit when all of. saidprivate relaysi are energized. I

4-. In combination, a plurality of telephone lines, a private relay foreach of said lines, a central exchange switchboard, a plurality of jacksmounted on said switchboard, operators cord circuits therefor, automaticswitches connected to said 'jacks, saidswitches having contactsconnected to said telephone lines, a circuit controlled by said privaterelay, a busy relay in said circuit, a signal, and means controlled bysaid last relay upon the insertion of a plug in one of said jacks whenall of said telephone lines are busy to display said signal 5. Incombination, a plurality of tele phone lines, automatic switches havingbanks of contacts at which said lines are connected, a central exchangeswitchboard, jacks mounted on said switchboard, operators cord circuitstherefor, a circuit controlled by the insertion of a plug in one of saidjacks, a selecting relay in said circuit, a stepping magnet for saidswitch, an interrupter in circuit with said stepping mag net, contactsin said interupter circuit controlled by said selecting relay, a busyrelay having contacts in said interrupter circuit,

private relays connected to each of said lines, said relays beingenergized when the corresponding line is busy, a series circuit closedby energization of all of said relays for energizing said busy relay toopen the contacts in the interrupter circuit.

6. In combination, a plurality of telephone lines, automatic switcheshaving banks of contacts at which said lines are connected, a central.exchange switchboard, jacks mounted on said switchboard, operatorsrcordcircuits therefon 'acircuit controlled by the insertion of a plug inone. of said jacks, a selecting relay in saidvcircuit, a stepping magnetfor said switch, an interrupter in circuit with said stepping magnet,contacts in said interrupter circuit controlled. by saidselecting relay,a busy-relay having contacts insaid interrupter circuit, private relaysconnected to each of said lines, said relays being energized when thecorresponding line is busy, a series circuit closedrby: energization ofall of said relays for-energizing said, busy relay tov open thecontacts-in the interrupter circuit, busy signals mounted on saidswitchboard adjacent each of said jacks, av circuit for said signal,contacts in said circuit controlled .by said busy relay. 1

7. In, combination, a plurality of tele-. phone lines, a centralexchange switchboard, jacks mounted on said switchboard, a plurality. ofautomatic switches each connected to one of said jacks, said switcheshaving selectablecontacts connected to said lines, a relay connected toeach line, saidrelay energizedwhen the corresponding line is busy, aist.pping magnet for said switch, aninterrupter circuit for said steppingmagnet, a selecting relayto close said interrupter circuit to move saidswitch, a contact controlledgby the insertion of a plug in thecorresponding jack to energize said selecting relay, a busy relay havinga circuit controlled in series by the relays connected to said lines, abusy test machine, a circuit for said machine, a contact in said circuitclosed bythe energization ofsaid busy re= lay, a, contact connected, toeach of said acks, saidcontact controlled by the;-corre pendingselecting relay to close the circuit of said busy test machine to thecord circuit;

Qf-the connectedplug to apprise the calling subscriber that all of saidselectable lines arebusy.

8.,1n combination, phone lines, a central exchange switchboard, a,plurality ofjacks mounted on said switch board, a plurality of calllnglines, acord circuit; to connect said calling lines with said j acks,automatic selecting switches connecteduto said jacks, csaid'switcheshaving banksofcontacts connectedito each of said telephone lines, astepping magnetrfor said switch, a selecting magnet controlling-the aplurality of telecircuit of said stepping magnet, private relaysconnected to thecontacts corresponding to each of said lines, a testingrelay, a contact for said testing relay controlled by said ting relay,said testing relay and said private relay being connected in series bysaid automatic switch and means controlled by said testing relay forplacing a test po tential upon said 'privatecontact corresponding to theselectedline, a busy relay, a circuit for said busy relay controlled bysaid private relay, a busy signal, a circuit forsaid signal, said busyrelay controlling the circuit of said signal and said interruptercircuit.

9. In combination, a plurality of tele phone lincs, a central exchangeswitchboard, a plurality of jacks mounted on said switchboard, automaticselecting switches connected to said jacks, said switches havingselectable contacts connected to said telephone 1 lines, a steppingmagnet, a circuit for said. magnet, a private'magnet for each telephoneline, a privaterelay for each telephone line, a selecting relay for eachjack, said relay being energized bythe insertion of a plug insaid'jack,a busy relay controlled bysaid private'relay and contacts in saidinterrupter'circuit controlledby said busy relay and said'selectingrelay respectively.

- 10. In combination, a plurality of telephone'lines, a'central exchangeswitchboard, a plurality or jacks mounted on-said switchboard,automaticswitches connected to said jacks, said switches havingselectable con tacts corresponding to each of said lines, said contactsincluding private contacts for each line, a selecting relay having acircuit controlled by the'insertion-of a: plug in the correspondingjack, e'ach of said lines hav ing a private relay connected'to thecorresponding private circuit, a circuit having a plurality of normallyopen contacts inseries, a busy relay in said-circuit, a metercontrolling relay having a circuit controlled by said busy relay, ameter, andmeans controlled by the energization of said meter controllingrelay for operating said meter.

11. In combination, a group of'telephone lines, a central exchangeswitchboard, jacks mountedfion said switchboard, operators connectingplugs, automatic switches connected to said jacks, said-switches havingselectable contacts connected to each of said lines, a private relay foreach line, said relay being energized upon the selection of said line byan automatic switch, a busy relay, a circuit for said'relay,-contacts insaid circuit controlled by said relay, other contacts in said circuitcontrolled by the insertion of aplug in one of said'jacks, a meter forsaid group of lines, and means for actuating saidnieter uponoperation-of said lllfitlGlYCOlltlOlllIlQ' relay.

12; In combination, a group of telephonelines, a busy relay for saidgroup of lines, a private relay for each of said lines, a c1rcu1t forsaid busy relay controlled by each of said private relays to causeoperation of said busy relay when all of said private relays areenergized, a meter controlling relay having a circuit controlled by saidbusy relay, a meter for said group of lines and operating means for saidmeter, said means controlled by said last named relay.

13. Incombination, a group of telephone lines, a central exchangeswitchboard, jacks for said telephone lines, operators connectingcircuits for said jacks, private relays for each of said lines, saidrelays being energized upon the connection of an operators connectingcircuit with the corresponding line, a busy group relay, said relayhaving a circuit controlled by each ofsaid pri vate relays, a meter, andmeans to operate said meter upon the actuation of said busy group relay.

14:. In combination, a group of telephone lines, a central exchangeswitchboard, jacks on said switchboard for said telephone lines, privaterelays for each of said lines, a busy group relay having a circuitcontrolled by said private relays, a meter controlling magnet having acircuit controlled jointly by said busy group relay, and by theinsertion of a plug in one of said jacks, and a group meter operatedupon the actuation of said meter controlling relay.

15. In combination, a group of telephone lines, a central exchangeswitchboard, a plurality of jacks for said lines, private magnets :toreach line, said magnets being energized when the corresponding lines arebusy, abusy group relay, a circuit for said relay controlled by each ofsaid private relays, a meter controlling relay, a low-wound relay, acircuit connecting said meter controlling relay and said low-wound relayin series, a normally open contact in said circuit, said contactcontrolled by said busy relay, means to close said circuit, said meansbeing oper ated by the insertion of a plug in one of said jacks, a busymeter for said group of lines, means controlled by the operation of saidmeter controlling relay to operate said meter and to short-circuit saidmeter-controlling relay to cause energization of said lowwound relay,said low-wound relay closing a locking circuit and breaking the circuitof i said meter-controlling relay.

16. I11 combination, a group of telephone lines, a central exchangemultiple switchboard, a plurality of selecting jacks mounted in regularnumerical order according to their directory numbers among the multipleson said switchboard, automatic line selecting switches connected to saidjacks, said switches having selectable contacts connected to said groupof lines, line relays connected to said lines, answering acks mounted onsaid central exchange switchboard connected to said lines, a linesignal, a cut-ofi relay, said relay being energized by the insertion ofa plug in said answering jack or by the connection of a plug with saidline through the selecting jack and automatic selecting switch. r i

17. In combination, a private branch ex-' change switchboard, a centralexchange multiple switchboard, a plurality of lines leading from saidprivate branch board to said central exchange board, and havinganswer'-' ing jacks in regular answering position in said centralswitchboard, selecting jacks mounted among the multiples in regularnumerical order according to'the given'directory number, automaticselecting switches connected to said selecting jacks and multipleterminals for said lines in said switches, said terminals beingselectable by said switches.

l8.' In combination, a private branch exchange switchboard, acentral'exchange multiple switchboard, a pluralityiof lines leading fromsaid private branch exchange board to said central exchange board andhaving answering jacks in regular answering position in said centralswitchboard, selecting jacks mounted among the mul'tiples in regularnumerical order according-to the given directory number, automaticselecting switches connected to said selecting jacks, multiple terminalsfor saidlines terminating in said automatic switches and means to recordthe number of times that a selection was attempted andall' the lineswere busy.

19. In combination, a private branch exchange switchboard, a centralexchange multiple switchboard, a plurality of lines be tween saidexchanges terminating in said switchboard, answering terminals normallyconnected to said linesiand multiple jacks normally disconnected fromsaid lines and an automatic switch for each jack to allow selection ofan idle line'and connection of the jack therewith: a

20. In combination, a private branchexchange switchboard, a centralexchange multiple switchboarcha plurality of lines ex tending betweensaid exchanges and having switchboard normally connected to said lines,multiple jacks normally disconnected from said lines and fromeach'other,'-and automatic switches for each jack to allow selection ofan idle line and connection of the corresponding jack therewith, saidjacks being all similarly numbered and located in the multiples.

21. In combination, a private branch exchange switchboard, a centralexchange multiple switchboard, a plurality of lines between saidswitchboards, a plurality of multiple jacks all corresponding inposition in the multiples to a single exchange or dir'ec-' I15 answeringterminals" at the central exchange tory number, said jacks beingnormally dis- In Witness whereof, I hereunto subscribe connected fromsaid lines, automatic selectmy name this 14th day of November, A. D. ining switches at the central exchange for 1914. making connection betweensaid jacks and .5 idle ones of said lines and means for registering thenumber of times when a selection Witnesses: Was attempted and all of thelines were GEO. V. LENNON, busy. C. H. McCoNNELL.

EUGENE A. REINKE.

(3035a: 01 this patent may be obtained for five cents each, byaddressing the Commissioner of Patents, Waehington, D. 0.

